N,P-Doped Molybdenum Carbide Nanofibers for Efficient Hydrogen Production.

Molybdenum (Mo) carbide-based electrocatalysts are considered promising candidates to replace Pt-based materials toward the hydrogen evolution reaction (HER). Among different crystal phases of Mo carbides, although Mo2C exhibits the highest catalytic performance, the activity is still restricted by the strong Mo-H bonding. To weaken the strong Mo-H bonding, creating abundant Mo2C/MoC interfaces and/or doping a proper amount of electron-rich (such as N and P) dopants into the Mo2C crystal lattice are effective because of the electron transfer from Mo to surrounding C in carbides and/or N/P dopants. In addition, Mo carbides with well-defined nanostructures, such as one-dimensional nanostructure, are desirable to achieve abundant catalytic active sites. Herein, well-defined N,P-codoped Mo2C/MoC nanofibers (N,P-Mo xC NF) were prepared by pyrolysis of phosphomolybdic ([PMo12O40]3-, PMo12) acid-doped polyaniline nanofibers at 900 °C under an Ar atmosphere, in which the hybrid polymeric precursor was synthesized via a facile interfacial polymerization method. The experimental results indicate that the judicious choice of pyrolysis temperature is essential for creating abundant Mo2C/MoC interfaces and regulating the N,P-doping level in both Mo carbides and carbon matrixes, which leads to optimized electronic properties for accelerating HER kinetics. As a result, N,P-Mo xC NF exhibits excellent HER catalytic activity in both acidic and alkaline media. It requires an overpotential of only 107 and 135 mV to reach a current density of 10 mA cm-2 in 0.5 M H2SO4 and 1 M KOH, respectively, which is comparable and even superior to the best of Mo carbide-based electrocatalysts and other noble metal-free electrocatalysts.